ERBB2 and metastatic neoplasm: Treating metastatic disease poses many challenges owing to a lack of knowledge of the critical molecular targets for therapy and to the acquisition of resistance both to standard chemotherapy and targeted therapies such as selective estrogen receptor modulators (SERMs) and the anti-HER2 (human epidermal growth factor receptor 2; also known as Erb-b2) antibody, trastuzumab (Eckhardt et al., 2012).